The true historical accuracy of the film lies not in the greater story, but in the details, given that the film was loosely based on a real incident and never claimed to tell a true story. When it comes to the story, the movie is based on the story of the Niland brothers, one of the cases of World War II that lead to the passing of the Sole Survivor Policy in 1948. Like Private Ryan, Frederick Niland was one of four enlisted brothers involved in the D-Day invasion of World War II, and like Ryan, Frederick was sent home to his parents after the army heard about the fate of his three brothers. Each of the brothers served in a different unit per regulation, the eldest, Technical Sergeant Edward, was a pilot in the Army Air Force and shot down over Burma in 1944 where he was presumed dead until a year later when he was found to be still be alive in a Burmese concentration camp. Preston was the second eldest and placed as a lieutenant in the 4th infantry where he was part of the first wave of invasions on the beach but was wounded and died on the Omaha the day after while Robert was placed in the 82nd Airborne as part of the parachute infantry and was killed on D-Day while manning his gun just off the beach during the first wave. 
Sergeant Frederick of the 101st Airborne parachute infantry on the other hand, was dropped between Omaha and Utah beaches and, contrary to Private Ryan, stayed with his unit until he received the paperwork from Chaplain Sampson of the 501st to be sent home, a unit was not sent to find him as in the movie. Niland stayed with his unit for a few days before being sent back to England, then to the U.S. where he continued to serve on the home front as Military Police in New York until after the war when he went to school to be a dentist.
In terms of other details, such as the beach scene and the emotions felt by the men, the movie mostly does a great job of showing off its historical accuracies. In this video I will talk a little about the accuracies in the opening scene of storming the beach based on statements made by veterans who had seen the movie, and gave their views on how the film made them feel.
By studying the historical accuracies, inaccuracies are bound to be uncovered. Aside from the aforementioned discrepancies in the Niland brothers story versus the Ryan brothers story in the movie, there are a few other things that are worth mentioning to make sure that there is a full analysis. The inaccuracies in the story make up a majority of the other inaccuracies of the film, leaving more subtle details under the scope of inaccurate things, such as the units travels, they are only shown traveling during the day, something that would have been dangerous to do at the time and place they were traveling through. This is one of a handful of minor inaccuracies that are covered by the changes in the story of the Niland brothers, things that are sacrificed to allow the story to carry the effect it needed, even when the story itself is only loosely based on the true event. When thinking about these inaccuracies however, it is important to remember that the movie is never advertised as a documentary and Spielberg never claims that every part of the movie is historically accurate, only that he did what he could to create a story set in World War II era France, loosely based on the story of the Niland brothers, whose experience helped lead to the creation of the Sole Survivor policy.
 United States Department of Defense Directive, Special Separation Policies for Survivorship. 1315.15, Sep 26, 1988.
 “WWII Display – The Niland Boys”, Canisius College, July 2006. https://web.archive.org/web/20120310220526/http:/www.canisius.edu/archives/niland.asp
Photo: “Niland Brothers- Saving Private Ryan”, DDay Overlord, Accessed November 10, 2020. https://www.dday-overlord.com/en/filmography/saving-private-ryan/niland-brothers
”Saving Private Ryan – The Real life D-Day Backstory” History.com, July 1, 2019. https://www.history.com/news/saving-private-ryan-real-life-dday-back-story
”WWII Display – The Niland Boys”, Canisius College, July 2006. https://web.archive.org/web/20120310220526/http:/www.canisius.edu/archives/niland.asp
Photo: Blake Stillwell, “This World War II Soldier was the Real Private Ryan” Mighty, April 29, 2020. https://www.wearethemighty.com/mighty-history/real-private-ryan/
 “Historical accuracy of WWII Films” world war ii films.weebly.com. https://worldwariifilms.weebly.com/saving-private-ryan.html#:~:text=Saving%20Private%20Ryan%2C%20directed%20by,War%20II%20films%20ever%20created.&text=This%20twenty%2Dfour%20minute%20battle,battle%20scene%20of%20all%20time.
Photo: Jeff Huston, “Saving Private Ryan (1998) 30+ Days of Spielberg” I can’t unsee that movie.com, June 18, 2016. https://icantunseethatmovie.com
 coqui1pr. “Saving Private Ryan D-Day Scene” Youtube video. 20 minutes 28 seconds. November 17, 2016. https://www.youtube.com/watch?v=X-bogN0V8RM
Saving Private Ryan, Directed by Stephen Spielberg. (July 24, 1998: Dreamworks and Paramount Pictures. 2004) DVD.
 Screen Slam. “Saving Private Ryan: Tom Hanks Exclusive Interview” Youtube Video. 6 minutes 58 seconds. February 20, 2018. https://www.youtube.com/watch?v=JSUnKN6ptlo
 CBSnews Staff. “Ryan too real for some Vets” CBS News. July 27, 1998. https://www.cbsnews.com/news/ryan-too-real-for-some-vets/
Nikola Budanovic. “Saving Private Ryan depicted war so Realistically that it Triggered PTSD among Veterans who Watched it” War History Online. May 11, 2018. https://www.warhistoryonline.com/world-war-ii/spielbergs-war-saving-private-ryan.html
 Roger Ebert. “Tom Hanks Recalls ‘Private Ryan’ Shoot” Roger Ebert.com. Interview from July 23, 1998. Accessed September 16, 2020. https://www.rogerebert.com/interviews/tom-hanks-recalls-private-ryan-shoot